He corrected that in the comment section of the youtube video. Six is actually the maximum amount. He just didn't want to buy another one.

He also published the Benchmarks in Detail and with two/four Macs in Comparison: https://github.com/geerlingguy/beowulf-ai-cluster/issues/17

> He just didn't want to buy another one.

Wasn’t it loaned ie didn’t buy any at all?

Apple should have loaned enough to flex.

Jeff mentioned in the video that only three of the ports can be used for RDMA. But it’s unclear where that limitation is coming from.

From my brief discussion with Exo/Apple, it sounds like that is just a limitation of this initial rollout, but it's not a hardware limitation.

Though, I am always leery to recommend any decisions be made over something that's not already proven to work, so I would say don't bet on all ports being able to be used. They very well may be able to though.

I bet there is one piece of silicon per two ports.